Currently, sublimation type thermal transfer recording method is known, in which a thermal transfer sheet comprising a colorant layer provided on one side of a substrate such as polyester film, the color layer comprising sublimation type dyes supported by a suitable binder is superposed on an image-receiving article, then another side of the substrate is allowed to be in contact with a thermal head so as to perform heat treatment by the thermal head, and thereby the sublimation type dyes are transferred to the image-receiving article. According to the sublimation type thermal transfer recording method, since it is possible to control the transferring amount of the sublimation type dye dot unit by dot unit with varying the amount of energy applied to the thermal transfer sheet, it is possible to perform a density gradation. Therefore, this method can provide a high quality image which is very vivid, and excels in the transparency, and the color reproducibility and the gradient of halftones, and which is comparable to full-color photograph image.
Incidentally, with respect to the thermal transfer sheet, when the printing is performed by contacting directly the thermal head directly to the substrate, a probable case that a sticking is caused by a frictional force generated between the substrate and the thermal head will arise, and this will result in printing failure. Further, there is a possibility that the substrate is fused to the thermal head by the heat during printing, and this fusion will prevent the travel of the thermal transfer sheet. As results, not only the sticking, but also the fracture of the sheet may arise in extreme cases. Accordingly, in the field of thermal transfer sheet, a backing layer which is provided on the other surface of the substrate for the purpose of improving the thermal resistance and giving the driving stability by imparting lubricity is usually adopted.
However, with respect to the backing layer for the purpose of driving stability, a problem that the residue derived from the components of the backing layer is accumulated around the heating element of the thermal head during the thermal transfer is inherent. If the residue is attached to the thermal head, there is a probably case that the heat from the thermal head will be not transmitted sufficiently to the thermal transfer sheet, and thus the formation of high-quality image can not be attained, and there is also a case that printing flaws due to the residue that has accumulated occurs. Further, in a printing condition where a concentrated solid printing portion and a gradation pattern portion of halftone are adjacent to each other among many printing conditions, when the heating energy applied to the thermal head is rapidly changed from the high level to the low level, a problem which seems to be the influence of residue that has been accumulated at the contact portion between the thermal head and the back face side of the thermal transfer sheet, and in which a dirt tailing (inconsistencies in density) arises in the gradation pattern portion of the halftone, will arise. Therefore, in the field of thermal transfer sheet, to prevent the residue of the backing layer attaching to the thermal head, or to prevent the attached residue accumulating to the thermal head, has become an important subject.
Under such a circumstance, for instance, in Patent Literature 1, a thermal transfer sheet which is provided with a back face layer containing an organic filler is disclosed. According to the thermal transfer sheet disclosed in the Patent Literature 1, there is no adhesion of residue to the thermal head, and it does not cause faulty transfer of the transcriptive protective layer. Further, in addition to this literature, various thermal transfer sheets each back face layer of which contains minute particles for removing the residue attached to the thermal head have also been proposed.